We plan to study the effect of overfeeding with carbohydrate on thermogenesis as indicated by metabolic rate and skin temperatures in young spontaneously obese subjects and to compare with previous studies of lean and reduced obese subjects. We also plan to measure the same in volunteers with experimental obesity resulting from overeating a mixed diet. In animal studies we will measure serial endocrine and metabolic changes during seasonal weight gain in woodchucks with indwelling arterial cannulae.